Defending National League champs are playing catch-up far below full strength

DENVER -- Right-hander Carlos Martinez is the poster boy for the challenges the St. Louis Cardinals are suddenly facing in their rotation.

Martinez opened the season as the eighth-inning go-to guy, but he struggled so much in May that he was removed from that late-inning setup role. And the next thing he knew, he was being asked to make a couple fill-in starts so the Cardinals could buy some extra rest for Adam Wainwright on June 16 and then Michael Wacha on Sunday.

Today?

Martinez is in the rotation, taking the place of Wacha, who, along with left-handed starter Jaime Garcia, went on the disabled list on Monday with shoulder problems. And Martinez, 22, who has only three starts in his 53 big league appearances, could well be considered the No. 3 starter behind Wainwright and Lance Lynn.

Think about it.

Marco Gonzales, the Cards' first-round pick in 2013, has been called up from Double-A Springfield to make his big league debut and start in place of Garcia in Wednesday's series finale against the Rockies.

And that comes on the heels of Shelby Miller having to depart in the third inning of Tuesday night's 10-5 loss to the Rockies at Coors Field because of "twinges" in his mid-back. Miller admitted the back issue could be related to the hip problem that forced him out of his previous start against Philadelphia.

Miller said he is confident that he can be ready for his next start -- Sunday against the Dodgers and Clayton Kershaw -- which would be a relief. The Cardinals, however, also know that a week ago, they were not talking about Wacha and Garcia being placed on the DL.

It's just another challenge for a Cards team that is in second place in the National League Central, 4 1/2 games back of the Brewers. Milwaukee has had a starter miss only one start so far this season, and the Crew has lost only 55 days to the disabled list for the entire starting lineup.

The defending NL champion Cardinals should be so fortunate.

"We're not focused on [the Brewers] too much," said Cards manager Mike Matheny. "I would be lying to say we are not watching them once in a while, but we have to just play good baseball. We have more than half the season remaining."

The question is during how much of what remains will the Cardinals have their rotation in place?

There is the anticipation that Joe Kelly could be back soon. Out since April 17 with a left hamstring strain, he makes his first Minor League rehab start on Friday. If all goes well, will St. Louis decide to rush Kelly back to start in San Francisco next week, or will the Redbirds be a bit more cautious and have him stretch out in another start or two in the Minors?

Two factors will play a part in answering that question.

How well will Gonzales handle the start at Coors Field, just an hour away from his hometown of Fort Collins, Colo., where he set a state record by pitching and winning the state baseball title game in all four years at Rocky Mountain High?

And how serious were the "twinges" that forced Miller's exit 17 batters and eight outs into his appearance against the Rockies?

While Miller talked optimistically about being ready for the game in Los Angeles, Matheny admitted "you're always concerned when someone comes out of the game."

Lynn was dominant in eight shutout innings on Monday at Coors Field after tweaking his windup to alleviate concerns that he had been tipping in his pitches, and Wainwright bounced back after missing a start on June 16 because of elbow inflammation to allow just one run in eight innings against Philadelphia on Saturday.

After that, however, a rotation that has an NL-best 3.06 ERA doesn't have a lot of sure things.

There has been talk about giving a look at Tim Cooney or Zach Petrick, who are at Triple-A Memphis, or even bringing back Tyler Lyons, who was in the rotation earlier in the season but went on the DL and was optioned back to Memphis when he was activated.

But when the Cards needed a starter for Wednesday, they called on Gonzales, even though he has pitched only 99 2/3 innings in pro ball, and has pitched in only seven games above Class A.

One of the others, however, would be likely to get a call if Miller has a setback and/or the Cardinals decide to give Kelly more than one rehab start.

"The big thing is to try and stay on top of it," said Miller. "After it happened in my last start, I waited a little. I have to try and stay hydrated and take care of my body. I don't think it is necessarily a big deal."

The Cards can only hope he is right.

Tracy Ringolsby is a columnist for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.